The present invention provides polyester polyols which may be used for the preparation of PUR pourable elastomers with, i.a. improved resistance to hydrolysis.
It is known to prepare PUR pourable elastomers by reacting polyester polyols with polyisocyanates. The polyester polyols have advantages over the well known polyether polyols, for example, they provide PUR elastomers with good overall mechanical properties in a particularly economic manner. The polyester polyol used in practice is often polyethylene adipate. Unfortunately, polyethylene adipate, like other polyester polyols, has the disadvantage that the elastomers prepared therefrom are susceptible to hydrolysis, which is prohibitive for many applications. In order to compensate for the disadvantage of susceptibility to hydrolysis of PUR elastomers, it is possible to add suitable anti-hydrolysis agents to the polyester polyols to be used, but this makes a corresponding production process less economic.
Moreover, in order to improve the resistance to hydrolysis of the polyester polyols to be used, it is technically possible to use relatively long-chain glycol and/or acid components to produce the polyester polyols, such as, for example, polybutylene adipate. Unfortunately, this is then associated with an increased risk of crystallisation during the preparation of the PUR elastomers. As a result, the elastomers obtained often have an undesirably high level of hardness at room temperature. Moreover, the high melting point of the polyester polyols having such a constitution is unfavourable for the processing thereof.
The object of the present invention was to provide polyester polyols from which it is possible to prepare PUR pourable elastomers which have good resistance to hydrolysis without the mechanical properties such as low temperature performance and impact resilience being impaired and which can be processed easily (long casting time with short solidification time of the PUR system used).
The invention provides, therefore, polyester polyols with an average equivalent weight (calculated from the experimentally determined OH value) in the range from 200 to 4000, prepared by reacting
a) xcex1,xcfx89-dicarboxylic acids or derivatives thereof with
b) butane 1,4-diol
c) hexane 1,6-diol
d) propane 1,3-diol or pentane 1,5-diol or a mixture thereof and
e) polyols having 3 to 6 hydroxyl groups,
component b) being used in amounts from 51 mole % to 85 mole %, component c) in amounts from 7 mole % to 25 mole %, component d) in amounts from 7 mole % to 25 mole % and component e) in amounts from 0.2 mole % to 2.5 mole %, based on the total amount of polyols b) to e).